Photovoltaic apparatus

ABSTRACT

A photovoltaic apparatus includes a first photoelectric conversion portion so formed on an insulating surface of a substrate as to cover a first substrate electrode and a second substrate electrode isolated from each other by a first groove, a second photoelectric conversion portion formed on the surface of the first photoelectric conversion portion through a conductive intermediate layer, a first back electrode and a second back electrode formed on the surface of said second photoelectric conversion portion and a connecting passage portion for electrically connecting the first substrate electrode and the second back electrode, provided at a prescribed interval from the side surface of said intermediate layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 11/708,050, which was filed Feb. 20, 2007 (allowed), which claimspriority to a Japanese application No. JP 2006-050523, filed on Feb. 27,2006. The entire disclosure of each of the referenced applications isherewith incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photovoltaic apparatus, and moreparticularly, it relates to a photovoltaic apparatus comprising aconductive intermediate layer between a plurality of photoelectricconversion portions.

2. Description of the Background Art

A photovoltaic apparatus comprising a conductive intermediate layerbetween a plurality of photoelectric conversion units (photoelectricconversion portions) is known in general, as disclosed in JapanesePatent Laying-Open No. 2002-118273, for example.

In the photovoltaic apparatus disclosed in the aforementioned JapanesePatent Laying-Open No. 2002-118273, first and second transparentelectrodes are formed on a substrate at a prescribed interval, while afirst photoelectric conversion unit is formed on the first and secondtransparent electrodes. A second photoelectric conversion unit is formedon the first photoelectric conversion unit through a conductiveintermediate layer. First and second back electrodes are arranged on thesecond photoelectric conversion unit to correspond to the aforementionedfirst and second transparent electrodes respectively. The first backelectrode is electrically connected to the second transparent electrodethrough a groove so formed as to pass through the second photoelectricconversion unit, the intermediate layer and the first photoelectricconversion unit.

In the photovoltaic apparatus disclosed in the aforementioned JapanesePatent Laying-Open No. 2002-118273, however, the first back electrode isin contact with the conductive intermediate layer in the groove, todisadvantageously result in an electrical short circuit between thefirst back electrode and the intermediate layer.

SUMMARY OF THE INVENTION

The present invention has been proposed in order to solve theaforementioned problem, and an object thereof is to provide aphotovoltaic apparatus, comprising a conductive intermediate layerbetween a plurality of photoelectric conversion portions, capable ofsuppressing an electrical short circuit between a back electrode and theintermediate layer.

In order to attain the aforementioned object, a photovoltaic apparatusaccording to an aspect of the present invention comprises a substratehaving an insulating surface, a first substrate electrode and a secondsubstrate electrode formed on the insulating surface of the substrateand isolated from each other by a first groove, a first photoelectricconversion portion so formed as to cover the first substrate electrodeand the second substrate electrode, a second photoelectric conversionportion formed on the surface of the first photoelectric conversionportion through a conductive intermediate layer, a first back electrodeand a second back electrode, formed on the surface of the secondphotoelectric conversion portion, corresponding to the first substrateelectrode and the second substrate electrode respectively, and aconnecting passage portion for electrically connecting the firstsubstrate electrode and the second back electrode, provided at aprescribed interval from the side surface of the intermediate layer.

In the photovoltaic apparatus according to the aforementioned aspect, ashereinabove described, the connecting passage portion for electricallyconnecting the first substrate electrode and the second back electrodeis provided at the prescribed interval from the side surface of theintermediate layer, whereby the connecting passage portion and theintermediate layer can be electrically isolated from each other.Therefore, the second back electrode and the intermediate layer can beelectrically isolated from each other. Thus, the second back electrodecan be inhibited from an electrical short circuit with the intermediatelayer.

The photovoltaic apparatus according to the aforementioned aspectpreferably further comprises a second groove so provided as to isolateat least the intermediate layer to expose the inner side surface of theintermediate layer and cover at least the inner side surface closer tothe first groove of exposed the intermediate layer with the secondphotoelectric conversion portion, and a third groove so formed as theconnecting passage portion at a position spaced at a prescribed intervalthrough the second photoelectric conversion portion inside the secondgroove from the inner side surface closer to the first groove of theintermediate layer, as to expose the surface of the first substrateelectrode. According to this structure, the third groove as theconnecting passage portion can be formed at the prescribed interval fromthe side surface of the intermediate layer by the second photoelectricconversion portion. Thus, the third groove and the intermediate layercan be electrically insolated from each other, whereby the second backelectrode and the intermediate layer can be electrically isolated fromeach other.

In this case, the photovoltaic apparatus preferably further comprises afourth groove for electrically isolating the first back electrode andthe second back electrode from each other, formed on a region on theside opposite to the first groove with respect to the third groove,wherein the second back electrode preferably fills up the third grooveformed at a position spaced at a prescribed interval from the inner sidesurface of the intermediate layer exposed in the second groove and ispreferably electrically connected to the first substrate electrode bycoming into contact with the surface of the first substrate electrodeexposed in the third groove. According to this structure, the secondback electrode filling up the third groove electrically isolated fromthe intermediate layer can be inhibited from an electrical short circuitwith the intermediate layer while the second back electrode and thefirst substrate electrode can be electrically connected to each other.

In the aforementioned structure comprising the fourth groove, the fourthgroove is preferably formed so as not to cut the intermediate layer.According to this structure, particles of the conductive intermediatelayer can be prevented from flying in all directions when the fourthgroove is formed dissimilarly to a case where a groove cutting theintermediate layer is provided. Therefore, the conductive particles canbe prevented from adhering to the inner side surface of the fourthgroove. Thus, the first back electrode can be prevented from anelectrical short circuit with the intermediate layer resulting fromadhesion of the conductive particles to the inner side surfaces of thefourth groove.

In this case, the fourth groove is preferably formed inside a regionformed with the second groove. According to this structure, the fourthgroove can be reliably so formed so as not to cut the intermediatelayer.

In the aforementioned structure in which the fourth groove is formedinside the region formed with the second groove, the fourth groove maybe so formed as to isolate the first back electrode and the second backelectrode from each other, and preferably pass through the secondphotoelectric conversion portion to expose the surface of the firstsubstrate electrode.

In the aforementioned structure comprising the fourth groove, the fourthgroove is preferably formed at a position spaced at a prescribedinterval through the second photoelectric conversion portion inside thesecond groove from the inner side surface on the side opposite to thefirst groove of the intermediate layer exposed in the second groove.According to this structure, the fourth groove can be easily formedwithout cutting the intermediate layer.

In the aforementioned structure comprising the second groove and thethird groove, the inner side surface on the side opposite to the firstgroove of the intermediate layer exposed in the second groove ispreferably also covered with the second photoelectric conversionportion. Thus, the inner side surface on the side opposite to the firstgroove of the intermediate layer can be spaced from the second backelectrode at the prescribed interval, whereby an electrical shortcircuit between the inner side surface on the side opposite to the firstgroove of the intermediate layer and the second back electrode can beinhibited.

In this case, the second photoelectric conversion portion may be soformed as to cover the inner side surface on the side opposite to thefirst groove of the first photoelectric conversion portion exposed inthe second groove in addition to the inner side surface on the sideopposite to the first groove of the intermediate layer exposed in thesecond groove.

In the aforementioned structure comprising the second groove and thethird groove, the second photoelectric conversion portion may be soformed as to cover the inner side surface closer to the first groove ofthe first photoelectric conversion portion exposed in the second groovein addition to the inner side surface closer to the first groove of theintermediate layer exposed in the second groove.

In the aforementioned structure comprising the second groove and thethird groove, the second groove may be so formed as to pass through theintermediate layer and the first photoelectric conversion portion andexpose the surface of the first substrate electrode.

The photovoltaic apparatus according to the aforementioned aspectpreferably further comprises a fifth groove so formed as to electricallyisolate the first back electrode and the second back electrode from eachother and pass through the second photoelectric conversion portion, theintermediate layer and the first photoelectric conversion portion, andincluding the connecting passage portion, an insulating member so formedas to cover at least the intermediate layer of the inner side surface onthe side of the second back electrode of the fifth groove, and aconductive member electrically connected to the first substrateelectrode with a surface exposed and electrically connected to thesecond back electrode across the insulating member in the connectingpassage portion located at a prescribed interval through the insulatingmember from the inner side surface on the side of the second backelectrode of the fifth groove. According to this structure, theconductive member formed in the fifth groove including the connectingpassage portion and the intermediate layer can be electrically isolatedfrom each other by the insulating member, whereby the second backelectrode and the intermediate layer can be electrically isolated fromeach other. Thus, the second back electrode can be inhibited from anelectrical short circuit with the intermediate layer.

In this case, the insulating member is preferably so formed as to coverthe overall inner side surface on the side of the second back electrodeof the fifth groove. According to this structure, the intermediate layerand the conductive member can be reliably electrically isolated fromeach other by the insulating member.

In the aforementioned structure comprising the conductive memberelectrically connected to the second back electrode across theinsulating member, the upper surface of the insulating member may be soformed as to project upward beyond the upper surface of the second backelectrode.

In the aforementioned structure comprising the conductive memberelectrically connected to the second back electrode across theinsulating member, the fifth groove preferably includes a sixth groovefor electrically isolating the first back electrode and the conductivemember in a region closer to the first back electrode in the fifthgroove, and forming a prescribed interval between the conductive memberformed in the connecting passage portion and the inner side surface onthe side of the first back electrode of the intermediate layer.According to this structure, the inner side surface on the side of thefirst back electrode of the intermediate layer and the conductive membercan be electrically isolated from each other, whereby an electricalshort circuit between the inner side surface on the side of the firstback electrode of the intermediate layer and the conductive member canbe inhibited.

In this case, the sixth groove may be so formed as to pass through thefirst back electrode, the second photoelectric conversion portion, theintermediate layer and the first photoelectric conversion portion andexpose the surface of the first substrate electrode.

In the photovoltaic apparatus according to the aforementioned aspect,the intermediate layer has a function of partly reflecting and partlytransmitting light incident from the side of the substrate.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the structure of a photovoltaicapparatus according to a first embodiment of the present invention;

FIGS. 2 to 9 are sectional views for illustrating a process ofmanufacturing the photovoltaic apparatus according to the firstembodiment shown in FIG. 1;

FIG. 10 is a sectional view showing the structure of a photovoltaicapparatus according to comparative example 1 with respect to the firstembodiment of the present invention;

FIG. 11 is a sectional view showing the structure of a photovoltaicapparatus according to a second embodiment of the present invention; and

FIGS. 12 to 14 are sectional views for illustrating a process ofmanufacturing the photovoltaic apparatus according to the secondembodiment shown in FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention are now described with reference tothe drawings.

First Embodiment

The structure of a photovoltaic apparatus 1 according to a firstembodiment of the present invention is now described with reference toFIG. 1.

As shown in FIG. 1, the photovoltaic apparatus 1 according to the firstembodiment comprises a substrate 2, substrate electrodes 3 a and 3 b, aphotoelectric conversion unit 4, an intermediate layer 5, anotherphotoelectric conversion unit 6 and back electrodes 7 a and 7 b. Thisphotovoltaic apparatus 1 according to the first embodiment is formed byserially connecting a plurality of units with each other in a directionalong the main surface of the substrate 2. The structure of thephotovoltaic apparatus 1 is now described in detail.

The substrate 2, having an insulating surface, consists of translucentglass. This substrate 2 has a thickness of about 1 mm to about 5 mm. Thesubstrate electrodes 3 a and 3 b isolated from each other by a groove 3c are formed on the upper surface of the substrate 2. The substrateelectrodes 3 a and 3 b, each having a thickness of about 800 nm, consistof TCO (transparent conductive oxide) such as tin oxide (SnO₂) havingconductivity and translucency. The substrate electrodes 3 a and 3 b areexamples of the “first substrate electrode” and the “second substrateelectrode” in the present invention respectively, and the groove 3 c isan example of the “first groove” in the present invention.

The photoelectric conversion unit 4 consisting of a p-i-n amorphoussilicon semiconductor is formed on the upper surfaces of the substrateelectrodes 3 a and 3 b. This photoelectric conversion unit 4 of thep-i-n amorphous silicon semiconductor is constituted of a p-typehydrogenated amorphous silicon carbide (a-SiC:H) layer having athickness of about 10 nm to about 20 nm, an i-type hydrogenatedamorphous silicon (a-Si:H) layer having a thickness of about 250 nm toabout 350 nm and an n-type hydrogenated amorphous silicon layer having athickness of about 20 nm to about 30 nm. The photoelectric conversionunit 4 is formed on the upper surface of the substrate electrode 3 a tohave a groove 4 a and fill up the groove 3 c. The photoelectricconversion unit 4 of the amorphous silicon semiconductor is formed forabsorbing light of a relatively short wavelength. This photoelectricconversion unit 4 is an example of the “first photoelectric conversionportion” in the present invention.

The intermediate layer 5 having a groove 5 a on regions corresponding tothe groove 4 a is formed on the upper surface of the photoelectricconversion unit 4. This intermediate layer 5 has a thickness of about 10nm to about 500 nm. The intermediate layer 5 consists of TCO such aszinc oxide (ZnO) having conductivity with a function of partlyreflecting and partly transmitting light incident from the side of thesubstrate 2. The intermediate layer 5 also has a function of increasingthe quantity of light passing through the photoelectric conversion unit4 by partly reflecting the light incident from the side of the substrate2. Therefore, an output current of the photoelectric conversion unit 4can be increased without increasing the thickness thereof. In otherwords, the output current of the photoelectric conversion unit 4 can beincreased while suppressing photo-deterioration remarkably increased inresponse to the thickness of the photoelectric conversion unit 4 of theamorphous silicon semiconductor. Thus, the output currents of thephotoelectric conversion units 4 and 6 can be balanced.

According to the first embodiment, the grooves 4 a and 5 a constitute agroove 20 a for electrically isolating portions of the intermediatelayer 5. The groove 20 a is an example of the “second groove” in thepresent invention.

According to the first embodiment, the photoelectric conversion unit 6of a p-i-n microcrystalline silicon semiconductor is formed on the uppersurface of the intermediate layer 5. This photoelectric conversion unit6 of the p-i-n microcrystalline silicon semiconductor is constituted ofa p-type hydrogenated microcrystalline silicon (μc-Si:H) layer having athickness of about 10 nm to about 20 nm, an i-type hydrogenatedmicrocrystalline silicon layer having a thickness of about 1500 nm toabout 2000 nm and an n-type hydrogenated microcrystalline silicon layerhaving a thickness of about 20 nm to about 30 nm. The photoelectricconversion unit 6 is formed to cover both inner side surfaces of thegroove 20 a and has grooves 6 a and 6 b in a region formed with thegroove 20 a. The photoelectric conversion unit 6 of the p-i-nmicrocrystalline silicon semiconductor is formed for absorbing light ofa relatively long wavelength. The groove 6 a is formed at a positionspaced at a prescribed interval through the photoelectric conversionunit 6 inside the groove 20 a from the inner side surface closer to thegroove 3 c of the groove 20 a, so as to expose the substrate electrode 3a. The photoelectric conversion unit 6 is an example of the “secondphotoelectric conversion portion” in the present invention, and thegroove 6 c is an example of the “third groove” and the “connectingpassage portion” in the present invention.

The back electrodes 7 a and 7 b isolated from each other by a groove 7 cformed on a region corresponding to the groove 6 b are formed on theupper surface of the photoelectric conversion unit 6. The backelectrodes 7 a and 7 b, each having a thickness of about 200 nm to about400 nm, consist of a metal material mainly composed of silver (Ag).These back electrodes 7 a and 7 b have a function of reflecting lightincident from the lower surface of the substrate 2 to reach the backelectrodes 7 a and 7 b, thereby reintroducing the same into thephotoelectric conversion units 4 and 6. The back electrode 7 a fills upthe groove 6 a and comes into contact with the surface of the substrateelectrode 3 a exposed in the groove 6 a, whereby the back electrode 7 ais electrically connected to the substrate electrode 3 a. Thus, thesubstrate electrode 3 a and the back electrode 7 b of the adjacent unitare serially connected with each other. The back electrodes 7 a and 7 bare examples of the “first back electrode” and the “second backelectrode” in the present invention respectively.

According to the first embodiment, the grooves 6 b and 7 d constitute agroove 20 b for electrically isolating the back electrodes 7 a and 7 bfrom each other. The groove 20 b is formed in a region formed with thegroove 20 a. The groove 20 b is formed at a position spaced at aprescribed interval through the photoelectric conversion unit 6 insidefrom the inner side surface on the side opposite to the groove 3 c ofthe groove 20 a so as to expose the substrate electrode 3 a. The groove20 b is an example of the “fourth groove” in the present invention.

A process of manufacturing the photovoltaic apparatus according to thefirst embodiment of the present invention is now described withreference to FIGS. 1 to 9.

As shown in FIG. 2, a substrate electrode 3 of tin oxide having athickness of about 800 nm is formed on the insulating upper surface ofthe substrate 2 by thermal CVD (chemical vapor deposition).

As shown in FIG. 3, the groove 3 c is formed by scanning the substrateelectrode 3 with a fundamental wave LB1 of an Nd:YAG laser having awavelength of about 1064 nm, an oscillation frequency of about 20 kHzand average power of about 14.0 W from above. Thus, the substrateelectrode 3 is separated into the substrate electrodes 3 a and 3 bthrough the groove 3 c.

As shown in FIG. 4, the photoelectric conversion unit 4 of the amorphoussilicon semiconductor is formed by successively forming the p-typehydrogenated amorphous silicon carbide layer having the thickness ofabout 10 nm to about 20 nm, the i-type hydrogenated amorphous siliconlayer having the thickness of about 250 nm to about 350 nm and then-type hydrogenated amorphous silicon layer having the thickness ofabout 20 nm to about 30 nm on the upper surfaces of the substrateelectrodes 3 a and 3 b by plasma CVD. At this time, the photoelectricconversion unit 4 is embedded in the groove 3 c. Thereafter theintermediate layer 5 of zinc oxide having the thickness of about 10 nmto about 500 nm is formed on the upper surface of the photoelectricconversion unit 4 by sputtering.

As shown in FIG. 5, the groove 20 a constituted of the grooves 4 b and 5b is formed to be adjacent to the groove 3 c by scanning thephotoelectric conversion unit 4 and the intermediate layer 5 with secondharmonics LB2 of an Nd:YAG laser having a wavelength of about 532 nm, anoscillation frequency of about 12 kHz and average power of about 230 mWfrom the side of the substrate 2.

Thereafter, as shown in FIG. 6, the photoelectric conversion unit 6 ofthe microcrystalline silicon semiconductor is formed by successivelyforming the p-type hydrogenated microcrystalline silicon layer havingthe thickness of about 10 nm to about 20 nm, the i-type hydrogenatedmicrocrystalline silicon layer having the thickness of about 1500 nm toabout 2000 nm and the n-type hydrogenated microcrystalline silicon layerhaving the thickness of about 20 nm to about 30 nm on the upper surfaceof the intermediate layer 5 by plasma CVD. At this time, thephotoelectric conversion unit 6 is embedded in the groove 20 a.

As shown in FIG. 7, the groove 6 a is formed at the position spaced atthe prescribed interval through the photoelectric conversion unit 6inside from the inner side surface closer to the groove 3 c of thegroove 20 a by scanning the photoelectric conversion unit 6 with secondharmonics LB3 of an Nd:YAG laser having a wavelength of about 532 nm, anoscillation frequency of about 12 kHz and average power of about 230 mWfrom the side of the substrate 2.

Thereafter, as shown in FIG. 8, the back electrode 7, having thethickness of about 200 nm to about 400 nm, of the metal material mainlycomposed of silver is formed on the upper surface of the photoelectricconversion unit 6 by sputtering. At this time, the back electrode 7 isembedded in the groove 6 a.

As shown in FIG. 9, the groove 20 b constituted of the grooves 6 b and 7c is formed at the position spaced at the prescribed interval throughthe photoelectric conversion unit 6 inside from the inner side surfaceon the side opposite to the groove 3 c of the groove 20 a by scanningthe photoelectric conversion unit 6 and the back electrode 7 with secondharmonics LB4 of an Nd:YAG laser having a wavelength of about 532 nm, anoscillation frequency of about 12 kHz and average power of about 230 mWfrom the side of the substrate 2. Thus, the back electrode 7 isseparated into the back electrodes 7 a and 7 b through the groove 20 a.

According to the first embodiment, as hereinabove described, the groove6 a for electrically connecting the substrate electrode 3 a and the backelectrode 7 b is provided at the prescribed interval through thephotoelectric conversion unit 6 inside the groove 20 a from the innerside surface closer to the groove 3 c of the intermediate layer 5,whereby the back electrode 7 b filling up the groove 6 a can beelectrically isolated from the portion of the intermediate layer 5.Thus, the back electrode 7 b can be inhibited from an electrical shortcircuit with the portion of the intermediate layer 5.

According to the first embodiment, the groove 20 b not cutting theintermediate layer 5 is provided, whereby particles of the conductiveintermediate layer 5 can be prevented from flying in all directions whenthe groove 20 b is formed dissimilarly to a case where an groove cuttingthe intermediate layer is provided. Therefore, the conductive particlescan be prevented from adhering to the inner side surfaces of the groove20 b. Thus, the back electrode 7 a can be prevented from an electricalshort circuit with the portions of the intermediate layer 5 resultingfrom adhesion of the conductive particles to the inner side surfaces ofthe groove 20 b.

According to the first embodiment, the groove 20 b is provided at theposition spaced at the prescribed interval through the photoelectricconversion unit 6 inside from the inner side surface opposite to theside of the groove 3 c of the groove 20 a, whereby the groove 20 b canbe easily formed without cutting the intermediate layer 5.

An experiment conducted for confirming the aforementioned effects of thefirst embodiment is now described. In this confirmatory experiment,photovoltaic apparatuses 1 and 101 according to Example 1 andcomparative example 1 were prepared as follows:

First, the photovoltaic apparatus 1 according to Example 1 was preparedas shown in FIG. 1, through the manufacturing process employed in thefirst embodiment. The photovoltaic apparatus 101 according tocomparative example 1 was prepared to have a structure shown in FIG. 10.At this time, a photoelectric conversion unit 104, an intermediate layer105, another photoelectric conversion unit 106 and back electrodes 107 aand 107 b of the photovoltaic apparatus 101 according to comparativeexample 1 were so formed as to have the same thicknesses andcompositions as those of a photoelectric conversion unit 4, anintermediate layer 5, another photoelectric conversion unit 6 and backelectrodes 7 a and 7 b of the photovoltaic apparatus 1 according toExample 1 respectively. Further, the photovoltaic apparatus 101according to comparative example 1 was formed with grooves 120 a and 120b corresponding to grooves 6 a and 20 b of the photovoltaic apparatus 1according to Example 1 respectively. According to comparative example 1,the back electrode 107 b was directly embedded in the groove 120 a, tobe electrically connected to a substrate electrode 3 a. The groove 120 belectrically isolates the back electrodes 107 a and 107 b from eachother while electrically isolating portions of the intermediate layer105 from each other.

As to the photovoltaic apparatuses 1 and 101 prepared according to theaforementioned Example 1 and comparative example 1, open circuitvoltages (Voc), short circuit currents (Isc), fill factors (F.F.),maximum power levels (Pmax) and conversion efficiency levels (Eff.) weremeasured and the results of the measurements were standardized withthose of the photovoltaic apparatus 101.

Table 1 shows the results.

TABLE 1 Open Short Circuit Circuit Fill Maximum Conversion VoltageVoltage Factor Power Efficiency Example 1 1.00 1.02 1.05 1.10 1.10Comparative 1.00 1.00 1.00 1.00 1.00 Example 1

Referring to Table 1, it has been proved that the open circuit voltageof the photovoltaic apparatus 1 according to Example 1 is identical tothat of the photovoltaic apparatus 101 according to comparativeexample 1. It has also been proved that the short circuit current andthe fill factor of the photovoltaic apparatus 1 according to Example 1are improved by 2% and 5% with respect to those of the photovoltaicapparatus 101 according to comparative example 1 respectively. It hasfurther been proved that the maximum power and the conversion efficiencyof the photovoltaic apparatus 1 according to Example 1 are improved by10% and 10% with respect to those of the photovoltaic apparatus 101according to comparative example 1 respectively.

The aforementioned results have conceivably been obtained for thefollowing reasons: In the photovoltaic apparatus 1 according to Example1 shown in FIG. 1, the photoelectric conversion unit 6 formed to coverthe inner side surfaces of the groove 20 a electrically isolates theback electrodes 7 a and 7 b from the portions of the intermediate layer5 for inhibiting the back electrodes 7 a and 7 b from an electricalshort circuit with the portions of the intermediate layer 5, therebyconceivably improving the conversion efficiency. In the photovoltaicapparatus 101 according to comparative example 1 shown in FIG. 10, onthe other hand, the back electrode 107 b embedded in the groove 120 a isin contact with the intermediate layer 5 in this groove 120 a to causean electrical short circuit with the intermediate layer 105, andparticles of the conductive intermediate layer 105 flying in alldirections when the groove 120 b is formed adhere to the inner sidesurfaces of the groove 120 b to cause an electrical short circuit of theback electrode 107 a and the intermediate layer 105, conceivablyresulting in reduction of the conversion efficiency.

Second Embodiment

Referring to FIG. 11, a photovoltaic apparatus 21 according to a secondembodiment of the present invention comprises an insulating member 28and a connecting electrode 29, in which the connecting electrode 29electrically connects a substrate electrode 3 a and a back electrode 7 bwith each other, dissimilarly to the aforementioned first embodiment.

In other words, this photovoltaic apparatus 21 according to the secondembodiment has a groove 24 a on the upper surface of a substrateelectrode 3 a, in which a photoelectric conversion unit 24 is formed tobe embedded in a groove 3 c as shown in FIG. 11. An intermediate layer25 having a groove 25 a on a region corresponding to the groove 24 a isformed on the upper surface of the photoelectric conversion unit 24. Anintermediate layer 26 having a groove 26 a on a region corresponding tothe groove 25 a is formed on the upper surface of the intermediate layer25. Back electrodes 27 a and 27 b isolated from each other by a groove27 c formed on a region corresponding to the groove 26 are formed on theupper surface of the photoelectric conversion unit 26. The photoelectricconversion unit 24, the intermediate layer 25, another photoelectricconversion unit 26, and the back electrodes 27 a and 27 b of thephotovoltaic apparatus 21 according to the second embodiment are soformed as to have the same thicknesses and compositions as those of thephotoelectric conversion unit 4, the intermediate layer 5, anotherphotoelectric conversion unit 6 and the back electrodes 7 a and 7 b ofthe photovoltaic apparatus 1 according to the aforementioned firstembodiment respectively.

According to the second embodiment, the grooves 24 b, 25 b, 26 b and 27d constitute a groove 40 for electrically isolating portions of theintermediate layer 25 from each other and electrically isolating theback electrodes 27 a and 27 b from each other. The groove 40 is anexample of the “fifth groove” in the present invention.

According to the second embodiment, an insulating member 28 is formed tocover the inner side surface on the side of the back electrode 27 b ofthe groove 40. The insulating member 28 consists of epoxy resincontaining aluminum oxide (Al₂O₃) particles. This insulating member 28is formed to cover the overall side surface on the side of the backelectrode 27 b of the groove 40. The upper surface of the insulatingmember 28 is so formed as to protrude upward beyond the upper surface ofthe back electrode 27 b. A connecting electrode 29 is formed in aconnecting passage portion 40 a located at a prescribed interval throughthe insulating member 28 from the inner side surface on the side of theback electrode 27 b of the groove 40. This connecting electrode 29 comesin contact with the surface of the substrate electrode 3 a exposed inthe connecting passage portion 40 a, whereby the connecting electrode 29is so formed to be electrically connected to the substrate electrode 3 aand to be electrically connected to the back electrode 27 b across theinsulating member 28. Thus, the substrate electrode 3 a and the backelectrode 27 b of the adjacent unit are serially connected with eachother. The connecting electrode 29 consists of conductive paste (silverpaste). The connecting electrode 29 is an example of the “conductivemember” in the present invention.

The groove 40 electrically isolates the back electrode 27 a and theconnecting electrode from each other on a region closer to the backelectrode 27 a of the groove and includes a groove 40 b for forming aprescribed interval between the connecting electrode 29 formed in theconnecting passage portion 40 a and the inner side surface on the sideof the back electrode 27 a of the groove 40. The groove 40 b is soformed as to pass through the back electrode 27 a, the photoelectricconversion unit 26, the intermediate layer 25 and the photoelectricconversion unit 24 and expose the surface of the substrate electrode 3a. The groove 40 b is an example of the “sixth groove” in the presentinvention.

A process of manufacturing the photovoltaic apparatus 21 according tothe second embodiment of the present invention is now described withreference to FIGS. 11 to 14. Steps up to formation of the groove 3 c inthe substrate electrode 3 are similar to those for the photovoltaicapparatus 1 according to the first embodiment shown in FIGS. 2 and 3.

According to the second embodiment, as shown in FIG. 12, thephotoelectric conversion unit 24 of the amorphous silicon semiconductoris formed on the upper surface of the substrate electrodes 3 a and 3 bto be embedded in the groove 3 c by plasma CVD. Thereafter theintermediate layer 25 is formed on the upper surface of thephotoelectric conversion unit 24 by sputtering. The photoelectricconversion unit 26 of the microcrystalline silicon semiconductor isformed on the upper surface of the intermediate layer 25 by plasma CVD.Thereafter the back electrode 27 is formed on the upper surface of thephotoelectric conversion unit 26 by sputtering.

According to the second embodiment, the photoelectric conversion unit24, the intermediate layer 25, the photoelectric conversion unit 26 andthe back electrode 27 are so continuously formed that the surfaces ofthe photoelectric conversion unit 24, the intermediate layer 25 and thephotoelectric conversion unit 26 are not exposed to the atmosphere.

As shown in FIG. 13, the groove 40 constituted of the grooves 24 a, 25a, 26 a and 27 a are formed to be adjacent to the groove 3 c by scanningthe photoelectric conversion unit 24, the intermediate layer 25, thephotoelectric conversion unit 26 and the back electrode 27 with secondharmonics LB5 of an Nd:YAG laser having a wavelength of about 532 nm, anoscillation frequency of about 12 kHz and average power of about 230 mWfrom the side of the substrate 2. Thus, the back electrode 7 isseparated into the back electrodes 7 a and 7 b through the groove 20 a.

As shown in FIG. 14, the insulating member 28 is applied by screenprinting, to cover the inner side surface on the side of the backelectrode 27 b of the groove 40 with the insulating member 28 and extendonto the back electrode 27 b. Thereafter, as shown in FIG. 11, theconnecting electrode 29 is applied to the connecting passage portion 40a located at the prescribed interval through the insulating member 28from the inner side surface on the side of the back electrode 27 b ofthe groove 40 by screen printing to cover the insulating member 28. Theconnecting electrode 29 comes into contact with the surface of thesubstrate electrode 3 a exposed in the connecting passage portion 40 a,whereby the connecting electrode 29 is electrically connected to thesubstrate electrode 3 a and electrically connected to the back substrate27 b across the insulating member 28. The groove 40 b is formed forelectrically isolating the back electrode 27 a and the connectingelectrode 29 on the region closer to the back electrode 27 a in thegroove 40 and forming the prescribed interval between the connectingelectrode 29 formed in the connecting passage portion 40 a and the innerside surface on the side of the back electrode 27 a of the groove 40.

According to the second embodiment, as hereinabove described, theinsulating member 28 covering the inner side surface on the side of theback electrode 27 b of the groove 40 is provided, and the connectingelectrode 29 for electrically connecting the substrate electrode 3 a andthe back electrode 27 b is provided at the prescribed interval throughthe insulating member 28 from the inner side surface on the side of theback electrode 27 b of the groove 40, whereby the connecting electrode29 formed in the connecting passage portion 40 a and the intermediatelayer 25 are electrically isolated from each other by the insulatingmember 28. Therefore, the back electrode 27 b and the intermediate layer25 can be electrically isolated from each other. Thus, the backelectrode 27 b can be inhibited from an electrical short circuit withthe intermediate layer 25.

According to the second embodiment, the connecting electrode 29 isprovided independently of the back electrode 27 so that a manufacturingprocess of subsequently forming the back electrode 27 after forming thephotoelectric conversion portion 26 and thereafter forming the groove 40while forming the connecting electrode 29 in the groove 40 can beemployed, whereby the surface of the photoelectric conversion unit 26,to be most inhibited from contamination in the process of manufacturingthe photovoltaic apparatus 21, can be prevented from exposure to theatmosphere.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

For example, while the groove 4 a of the photoelectric conversion unit 4and the groove 5 a of the intermediate layer 5 constitute the groove 20a electrically isolating the portions of the intermediate layer 5 in theaforementioned the first embodiment, the present invention is notrestricted to this but at least a groove cutting the intermediate layermay be alternatively formed to electrically isolate the same.

While the insulating member does not fill up the groove 40 b forelectrically cutting the back electrode 27 a and the connectingelectrode 29 in the aforementioned second embodiment, the presentinvention is not restricted to this but the insulating member may fillup the groove 40 b for electrically cutting the back electrode 27 a andthe connecting electrode 29.

1. A photovoltaic apparatus comprising: a substrate having an insulatingsurface; a first substrate electrode and a second substrate electrodeformed on said insulating surface of said substrate and isolated fromeach other by a first groove; a first photoelectric conversion portionso formed as to cover said first substrate electrode and said secondsubstrate electrode; a second photoelectric conversion portion formed onthe surface of said first photoelectric conversion portion through aconductive intermediate layer; a first back electrode and a second backelectrode, formed on the surface of said second photoelectric conversionportion, corresponding to said first substrate electrode and said secondsubstrate electrode respectively; and a connecting passage portion forelectrically connecting said first substrate electrode and said secondback electrode, provided at a prescribed interval from the side surfaceof said intermediate layer.
 2. The photovoltaic apparatus according toclaim 1, further comprising: a fifth groove so formed as to electricallyisolate said first back electrode and said second back electrode fromeach other and pass through said second photoelectric conversionportion, said intermediate layer and said first photoelectric conversionportion, and including said connecting passage portion; an insulatingmember so formed as to cover at least said intermediate layer of theinner side surface on the side of said second back electrode of saidfifth groove; and a conductive member electrically connected to saidfirst substrate electrode with a surface exposed and electricallyconnected to said second back electrode across said insulating member insaid connecting passage portion located at a prescribed interval throughsaid insulating member from the inner side surface on the side of saidsecond back electrode of said fifth groove.
 3. The photovoltaicapparatus according to claim 2, wherein, said insulating member is soformed as to cover the overall inner side surface on the side of saidsecond back electrode of said fifth groove.
 4. The photovoltaicapparatus according to claim 2, wherein the upper surface of saidinsulating member is so formed as to project upward beyond the uppersurface of said second back electrode.
 5. The photovoltaic apparatusaccording to claim 2, wherein said fifth groove includes a sixth groovefor electrically isolating said first back electrode and said conductivemember in a region closer to said first back electrode in said fifthgroove, and forming a prescribed interval between said conductive memberformed in said connecting passage portion and the inner side surface onthe side of said first back electrode of said intermediate layer.
 6. Thephotovoltaic apparatus according to claim 5, wherein said sixth grooveis so formed as to pass through said first back electrode, said secondphotoelectric conversion portion, said intermediate layer and said firstphotoelectric conversion portion and expose the surface of said firstsubstrate electrode.